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y Green River u E W Y D M I N G c • '`•__' Linwood Dutch John 1 Brown I s Park Ashley Dom t 9r;d C0 ADO 4 ? u T A H f r` J J I L? -rDINOSA ' NOTL t R i J MONUMENT r'ompp Vernal r` Jensen I ? Peen ce, G fede•41 C'Sphics, I.C. In the map above, lighter stippling indicates the louver portion of the Green River in which rotenone was used preliminary to stocking the Flaming Gorge Reservoir, now filling, with sport fish. When full, the reservoir trill extend from Ashley Dam nearly to Green River, Wyorning. Rotenone teas introduced into the Green River from its headwaters (far to the north in Wyoming, not shown on map) and its tributaries above Ashley Dam, nearly to the dam itself. A detosificntion station was to 1taa:e been set up at the base of Ashley Dam; actually,-it •aw_se1 _,? ?, Rra.,-n's Park Ilrideee, only 16 m-P-esabore the northern boundary of Dinosaur ' tional Monument. Failure of the e carton attempt caused heavy destruction of aquatic life in the Green River above and through the monument, and at least as for south as Jensen Bridge near Jensen, Utah (that portion of the river indicated by heavier shedinr). claimed that, withoul the "rehabilita- tion" project, Flaming Gorge Reser- voir would provide ideal conditions for a coarse-fish population explosion, and that it was also necessary- to treat trib- utaries to prevent "recontamination" or "reinfestation" of their natural en- vironment by the native, as well as the introduced, kinds. Unquestionably, there is evidence to support the bv- poth,esis that some native as well as in- troduced fishes do compete with certain prized garnefishes, and that a reduc- tion in the population of such competi- tors, followed by appropriate stocking, has led at least temporarily to increase -occasionally to spectacular increase- -in the angler's catch. In appro,,inr such measures, however, blologlsts should balance the possible harmful effects against the benefits, which typi- cally are of short duration. The Colorado River basin, of which Green River is a major tributary, con- tains a higher percentage of endemic species than does any other river in Western 'forth America. Eighty-seven percent of its native, freshwater fishes are found nowhere else. Some of the most unique of these animals are nom- seriously threatened with extinction from man's activities. Included in the section of Green River that was af- fected by this poisoning project were places ideal for the maintenance of four of these rare kinds- the Colorado squawfish (Ptychochedus _Lcius); the humpback chub (Gila cypha); the swift-river form of the bluehead sucker (Pantosteus delphinus), and the bump- back sucker (Xyrauchen texanus). The squavcfish is the largest member of the minnow family in this hemisphere and one of the largest in the world, once attaining lengths approaching six feet and weights nearing 100 pounds. The humpback chub is one of the most bi- arre fishes of this continent, being ex- traordinarily specialized for life in tor- rentially swift waters. The swift-water form of the bluehead sucker is likewise admirably adapted, and the humpback sucker is similarly specialized, but is the least threatened of the four. Study of Colorado Sgaawfish During the past thirteen years 1 have gathered information on the former size and abundance of the squawfish. on its present distribution in the Colo. rado River basin, and on anything I could learn of its life historv. AL the time of the poisoning, the on]), place known where the species could be taken in abundance was in the. Green River, from Hideout Canyon (eighteen river miles above Ashley Dam) down throu-h Dinosaur National Monument and in the lower part of its major trib- utary, the Yampa River of Colorado. The humpback chub similarly was common only in the swift portions of the Green River and in suitable trib- utaries. The status of these fisher: in the Green River is now uncertain and vrill not be known until careful surveys are made. 6 NATIONAL PARKS MAGAZINE